DS2746 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS2746

Low-Cost 2-Wire Battery Monitor with Ratiometric A/D Inputs

Dallas Semiconductor -> Maxim Integrated 

DS2746 Low-Cost 2-Wire Battery Monitor

Table 3. Accumulated Current Range for Various RSNS Values

VSS - VSNS

409.6mVh

20mΩ

20.48Ah

ACR RANGE

15mΩ

27.31Ah

RSNS

10mΩ

40.96Ah

5mΩ

81.92Ah

CURRENT OFFSET BIAS

The Current Offset Bias register (COBR) allows a programmable offset value to be added to raw current

measurements. The result of the raw current measurement plus the COBR value is displayed as the current

measurement result in the CURRENT register, and is used for current accumulation. The COBR value can be used

to correct for a static offset error, or can be used to intentionally skew the current results and therefore the current

accumulation.

Read and write access is allowed to COBR. Whenever the COBR is written, the new value is applied to all

subsequent current measurements. COBR can be programmed in 1.56μV steps to any value between +198μV and

-200μV. The COBR value is stored as a two’s complement value in volatile memory, and must be initialized via the

interface on power-up. Figure 10 describes the COBR address, format, and resolution.

Figure 10. Current Offset Bias Register Format

Address 61h

S 26 25 24 23 22 21 20

MSb

“S”: sign bit

LSb

Units: 1.56μV/Rsns

CURRENT BLANKING

The Current Blanking feature modifies current measurement result prior to being accumulated in the ACR. Current

Blanking occurs conditionally when a current measurement (raw current + COBR) falls in one of two defined

ranges. The first range prevents charge currents less than 100μV/RSNS from being accumulated. The second range

prevents discharge currents less than 25μV/RSNS in magnitude from being accumulated. Charge current blanking is

always performed, however, discharge current blanking must be enabled by setting the NBEN bit in the

Status/Config register. See the register description for additional information.

ACCUMULATION BIAS

The Accumulation Bias register (ABR) allows a programmable offset value to be added to the current accumulation

process. The new ACR value results from the addition of the Current register value plus ABR plus the previous

ACR value. ABR can be used to intentionally skew the current accumulation to estimate system stand-by currents

that are too small to measure. ABR value is not subject to the Current Blanking thresholds.

Read and write access is allowed to the ABR. Whenever the ABR is written, the new value is applied to all

subsequent current measurements. ABR can be set to any value between +193.75μV and -200μV in 6.25μV steps.

The ABR value is stored as a two’s complement value in volatile memory, and must be initialized via the interface

on power-up. The lower two bits of the ABR register have no effect on the data. Figure 11 describes the ABR

address, format, and resolution.

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